package com.zwh.common.utils.file;
// Copyright (C) 2002 by Jason Hunter <jhunter_AT_acm_DOT_org>.
// All rights reserved.  Use of this class is limited.
// Please see the LICENSE for more information.
import java.io.File;
import java.io.IOException;


/**
 * Implements a renaming policy that adds increasing integers to the body of
 * any file that collides.  For example, if foo.gif is being uploaded and a
 * file by the same name already exists, this logic will rename the upload
 * foo1.gif.  A second upload by the same name would be foo2.gif.
 * Note that for safety the rename() method creates a zero-length file with
 * the chosen name to act as a marker that the name is taken even before the
 * upload starts writing the bytes.
 *
 * @author Jason Hunter
 * @version 1.1, 2002/11/05, making thread safe with createNewFile()
 * @version 1.0, 2002/04/30, initial revision, thanks to Yoonjung Lee
 *                           for this idea
 */
public class MyFileNamePolicy {

    // This method does not need to be synchronized because createNewFile()
    // is atomic and used here to mark when a file name is chosen
    public File rename(File f) {
        if (createNewFile(f)) {
            return f;
        }
        String name = f.getName();
        String body = null;
        String ext = null;

        int dot = name.lastIndexOf(".");
        if (dot != -1) {
            body = name.substring(0, dot);
            ext = name.substring(dot);  // includes "."
        }
        else {
            body = name;
            ext = "";
        }

        // Increase the count until an empty spot is found.
        // Max out at 9999 to avoid an infinite loop caused by a persistent
        // IOException, like when the destination dir becomes non-writable.
        // We don't pass the exception up because our job is just to rename,
        // and the caller will hit any IOException in normal processing.
        int count = 0;
        while (!createNewFile(f) && count < 9999) {
            count++;
            String newName = body + count + ext;
            f = new File(f.getParent(), newName);
        }

        return f;
    }

    private boolean createNewFile(File f) {
        try {
            return f.createNewFile();
        }
        catch (IOException ignored) {
            return false;
        }
    }
}

